Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$175.61	5.383%	$185.0631	$185.06	$185.05	$185.10
Purchase #2	$33.34	7.305%	$35.7755	$35.78	$35.80	$35.80
Purchase #3	$177.72	11.863%	$198.8029	$198.80	$198.80	$198.80
Purchase #4	$248.30	12.461%	$279.2407	$279.24	$279.25	$279.20
Purchase #5	$126.75	13.764%	$144.1959	$144.20	$144.20	$144.20
Purchase #6	$187.79	4.823%	$196.8471	$196.85	$196.85	$196.80
Purchase #7	$232.89	4.819%	$244.113	$244.11	$244.10	$244.10
7 purchase totals =	$1,182.40		$1,284.0382	$1,284.04	$1,284.05	$1,284.00